This application relates to a regulator valve that sets the supply pressure in a hydraulic actuation system. This regulator valve manages the output flow from two gear pumps.
Regulator valves are used in any number of applications. In general, a regulator valve primarily consists of a valve sleeve, spool, and a spring. Valve porting and spring load is defined to achieve a desired pressure setting range over various load conditions (i.e., flow demand). The magnitude of a set pressure is the direct result of the valve spool area and balance of forces acting on the spool at any given hydraulic load condition, which include the spring force and pressure forces acting on the valve spool.
In one example, a main pump supplies hydraulic fluid to an actuator to control the pitch of a propeller. The main pump is capable of supplying sufficient fluid flow to meet much of the operational requirements of the actuator.
However, under transient conditions, the main pump may not be capable of supplying sufficient fluid flow to achieve the desire actuator performance requirements. Thus, a standby pump is also provided that can supplement the hydraulic fluid provided by the main pump to meet actuator performance requirements. The standby pump has an outlet connected to a regulator valve, and is also connected to a supply line downstream of the main pump through a check valve.
During low system flow demand conditions, the regulator valve will return the full standby pump flow to a sump, while a main metering window of the valve controls the system pressure setting by porting unused main pump flow to a sump. During high system flow demand conditions, the regulator valve spool repositions to close the main metering window of the regulator valve. This repositioning is caused by a change in the spool force balance due to a decrease in system pressure that occurs when system flow demand exceeds the main pump output. This valve spool translation continues until the main metering window closes the flow path to sump, and the standby metering window closes adequately to increase standby pump pressure to overcome a check valve pressure setting. At this point, the standby pump flow supplements the main pump flow, the main metering window is closed, and the system pressure setting is controlled by the regulator valve standby metering window in the same manner as described for the main metering window at low system flow demand conditions.
The regulator valve main metering port vents the unused main pump flow to the sump during low flow demand conditions. In the prior art, the main pump vent extended radially outwardly through a valve window opening established by a valve spool land edge and valve sleeve port. Cavitation bubble formation has occurred on the low pressure side of this radial discharge window configuration caused by localized pressure gradients that are of a magnitude less than the hydraulic system fluid vapour pressure. The subsequent collapse of formed bubbles on the surface of the main housing sump bore where vented flow is discharged is undesirable.